Production of alkyl benzenes

ABSTRACT

Process for the production of alkyl benzenes wherein norbornenes are passed under superatmospheric pressure through a hydrogenation catalyst in the presence of hydrogen at a relatively low temperature i.e. 50*-250*C. and then passed through a reforming catalyst at a higher temperature i.e. 400*600*C. and the alkyl benzenes are recovered.

United States Patent [1 1 Lorette 1 PRODUCTION OF ALKYL BENZENES [75] Inventor: Nicholas Bernard Lorette, Lake Jackson, Tex.

[73] Assignee: The Dow Chemical Company,

Midland, Mich.

221 Filed: May 26,1972

21 Appl. N0.: 257,102

[52] US. Cl..... 260/668 D, 260/666 PY, 260/668 R [51] Int. Cl. C07c 5/18, C070 5/02 [58] Field of Search 260/668 R, 668 D,

[56] References Cited UNITED STATES PATENTS 359L647 7/l97l Kochi et al. 260/666 PY I45] Sept. 11, 1973 3,629,348 l2/l97l Courduvelis et al 260/666 PY Primary Examiner-Curtis R. Davis Attorney-William M. Yates et al.

[57] ABSTRACT 12 Claims, No Drawings l PRODUCTION OF ALKYL BENZENES BACKGROUND OF THE INVENTION This invention relates to a process for the production dition of ethylene to cyclopentadiene. However, it is also known from Herndon et al., J. Physical Chemistry 68: 2016-2018 (1964) that norbornene decomposes at 350C. back into the above compounds.

It is also known from U. S. Pat. No. 2,754,339 that bicyclic terpenes such as alpha pinene can be converted (i.e. dehydrogenated) almost exclusively to aromatic terpenes such as p-cymene with small amounts of trimethyl benzenes."

It was thus surprising to find that norbornenes could be converted i.e. reformed into valuable alkyl benzenes having the same number of carbon atoms at temperatures greater than about 400C. if they were first hydrogenated.

SUMMARY OF THE INVENTION It now has been discovered that alkyl benzenes can be prepared by a process in which norbomenes in the presence of from about 3 to about moles of hydrogen per mole of norbornene are first passed at a liquid hourly space velocity (LHSV) of about 0.5 to about 5.0, a pressure from about 50 to 400 pounds per square inch gage (psig) and a temperature from about 50 to about 250C. through a hydrogenation catalyst which is effective to hydrogenate olefinic unsaturation. The effluent from this hydrogenation reaction is then passed, under the same velocity and pressure conditions, through a reforming catalyst effective to convert saturated carbocyclics to aromatics at a temperature from about 400 to about 600C. and the alkyl benzenes are recovered.

The norbomenes are melted or dissolved in a hydrocarbon solvent before theyare hydrogenated. It is preferred to dissolve the norbomenes in a solvent therefor The process is carried out in a single pass over the catalysts to achieve a high conversion with a high yield of alkyl benzenes. Recycling of the hydrogenated norbornenes gives higher conversion and higher yields.

The process can be conducted in a single reactor having a layered catalyst bed with the active catalyst beds in opposite ends thereof separated by an inert support material.

Alternatively, the process can be conductedin two separate reactors with the hydrogenation catalyst in the first reactor and the reforming catalyst located in the other"reactor.

' DETAILED DESCRIPTION The norbomenes which can be used in this invention are norbornene, -5-methyl-2-norbornene, 5ethyl-2- norbornene, norbornadiene, 5-methyl-2,5- norbornadiene, S-ethyl-2,5-norbornadiene, and related compounds.

These. norbomenes are combined with about 3 to about 15 moles of hydrogen per mole of hydrocarbon feed',:preferably from about 4to about 12 moles of hydrogen, over a hydrogenation catalyst which is effective to hydrogenate olefmic unsaturation. The catalysts used are those which are well known to those skilled in the art and are commercially available.

Typical catalysts contain 0.15-5 percent platinum supported on a refractory support such as alumina. Other metals that can be used are palladium, rhodium, rhenium, and thelike.

The catalysts used for the hydrogenation step are preferably also used for the reforming step. If desired, different commercial catalysts can be used for the reforming step. Typical catalysts of this type are platinum, palladium and rhenium.

The aforementioned norbornenes are either melted or dissolved in a hydrocarbon solvent before they are hydrogenated. The amount of solvent used is about 50 to about volume percent. Typical hydrocarbon solvents are saturated aliphatic solvents such as petroleum ether and naph'thas and the like, and carbocyclic solvents such as cyclohexane, diethylcyclohexane, methylcyclopentane, methylcyclohexane and the like.

The temperature in the hydrogenation zone is maintained at a temperaturefrom about 50 to about 250 with the preferred range being from about to about 250C. i

The norbomenes together with the hydrogen gas is passed through the hydrogenation catalyst at a liquid hourly space velocity from about 0.5 to about 5.0 and preferably in the range from about 0.5 to about 3.0.

The pressure in the hydrogenation zone is maintained in the range from about 50 to about 400 pounds per square inch gauge with the preferred pressure being in the range from about l75 to about 300 psig.

After the hydrogenation reaction the effluent is passed directly, under the same velocity and pressure conditions to a reforming zone having a catalyst therein effective to convert saturated carbocyclics to aromatics. The temperature of the reforming zone is maintained at a temperature from about 400 to about 600C. and preferably from about 425 to about 525C.

Following the hydrogenation and reforming steps, the reaction mixture is separated by distillation to yield the desired aromatics.

The following examples are presented to illustrate but not limit the invention.

EXAMPLES I AND 2 A one inch external diameter stainless steel pipe 38 inches long having a volume of 400 cc. was packed with cc. of a commercial 0.5 weight per cent platinum catalyst supported on 1/ 16 inch alumina extrusions. One hundred cubic centimeters of this catalyst was placed in the lower third of the reactor and 50 cc. was placed in the upper third of the reactor. Alpha alumina balls V4 inch in diameter were placed in the reactor below, between, and above the catalyst layers to provide a layered catalyst bed. a

The reactor tube was wrapped and heated by resistance wires to provide an upper catalyst zone heated to 200C. 1 10 and a lower catalyst zone heated to 430C. i 20.

A mixture of,80.0' weight per cent diethylcyclohexane and 20.0 weight percent norbornene in the presence of hydrogen gas was fed into the upper part of the TABLE I.CONVERTING NORBORNENE EXAMPLE 4 Following the procedure of Example l using a single catalyst bed operating at 220C., 5-methyl-2- norbornene was treated and analyzed to give the following results.

Temp. C Norbornene Mol Yield NB 1 Upper Lower converratios toluseleczone zone LHSV sion Hg/NB one tivity Example:

'Norbornene.

' EXAMPLE 3 Compound Moles 1n Moles Out cyclohexane 3.32 3.25 Following the procedure of Examples 1 and 2 nor- S-methfl- (1713 (1011 bornadiene (no solvent) was passed through the cata- 8'33? lyst zones, the conditions and results are reported in dimethylcyclohexanes 0153 Table I.

In order to verify and confirm the foregoing examples the following experiments were conducted.

EXPERIMENT 1 A reactor similar to that used in Example 1 was packed with 150 cc. of 0.5 percent platinum on 1/ 16 inch alumina extrusions. The remainder of the reactor This experiment shows that norbornene cannot be reformed directly into toluene with any practical degree of success.

EXPERIMENT 2 Using the same reactor as in Experiment 1, 88.3 percent cyclohexane mixed with 1 1.7 percent norbornene was passed through the catalyst bed operating at a temperature of 220C. The l-l /hydrocarbon mole ration was 3, the LHSV was 0.8 and the pressure was 225 psig.

The results are shown below:

Compound Moles 1n Moles Out cyclohexane 6.18 6.14 norbornene 0.72 norbomane 0.71

From a consideration of Experiments 1 and 2 it is evident that in Examples 1-3 the norbornenes are first hydrogenated and saturated in the low temperature catalyst zone and then the formed norbornanes are re-' formed into aromatics in the in the second or higher temperature zone. Furthermore, it is apparent that the reforming step (Experiment No. 1) cannot be directly applied to norbornenes.

The desired 2-methyl-norbornane was then distilled from the recovered mixture diluted with additional cyclohexane, and recycled back to the same catalyst bed under the same conditions except that the catalyst bed was heated to 465C. After recovery and analysis of the products, the results were found to be as follows.

Compound Moles In Moles Mole I: Out Yield cyclohexane 2.47 0.56 benzene 1.74 91.2 Z-methylnorbornane 0.381 0.001 dimethylcyclohexane 0.143 0.031 ethylcyclohexane 0.01 l ethyl benzene 0.062 12.89 p-xylene 0.040 8.32 m-xylene 0.144 29.94 o-xylene 0.137 28.48 toluene 0.01 1 2.28 based on the cyclohexane converted EXAMPLE 5 Following similar conditions of Example 4, 5-ethyl-2- norbornene was treated to form S-ethyl-norbornane which was then recovered and fed back with additional solvent to the same catalyst bed heated toa highertem- I claim: l. A process for the production of alkyl benzenes which comprises a. passing norbornenes in the presence of from about 3 to about 15 moles of hydrogen per mole of hydrocarbon feed at a LHSV of from about 0.5 to about 5.0 and a pressure from about50 to about 400 psig through a hydrogenation catalyst effective to hydrogenate olefmic unsaturation at a temperature from about 50 to about 250C;

b. passing the effluent under the same Ll-lSV and pressure conditions through a reforming catalyst effective to convert saturated carbocyclics to aromatics at a temperature from about 400 to about 600C., and c. recovering the alkyl benzenes. 2. The process as set forth in claim 1 wherein the norbornenes are dissolved in a hydrocarbon solvent.

3. The process as set forth in claim 2 wherein the norbornenes are dissolved in a carbocyclic solvent.

4. The process as set forth in claim 3 wherein norbornene is treated.

5. The process as set forth in claim 3 wherein 5-methyl-2-norbomene is treated.

6. The process as set forth in claim 3 wherein S-ethyl- 2-norbornene is treated.

7. The process as set forth in claim 3 wherein norbornadiene is treated.

8. A process for the production of alkyl benzenes which comprises a. passing norbornenes, in the presence of from about 4 to about 12 moles of hydrogen per mole of hydrocarbon feed, at a LHSV of from about 0.5 to about 5.0 and a pressure from about 175 to about 300 psig through a hydrogenation catalyst effective to hydrogenate olefinic unsaturation at a temperature from about 100 to about 225C.,

b. passing the effluent under the same LHSV and pressure conditions through a reforming catalyst effective to convert saturated carbocyclics to am matics at a temperature from about 425 to about 525C. and

c. recovering the alkyl benzenes.

-9. The process as set forth in claim 8 wherein the norbornenes are dissolved in a carbocyclic solvent.

10. The'process as set forth in claim 7 wherein the norbornenes are dissolved in about 50 to about mole percent of a carbocyclic solvent.

11. The process as set forth in claim 7 wherein the carbocyclic solvent is cyclohexane.

12. The process as set forth in claim 7 wherein the carbocyclic solvent is diethyl cyclohexane.

* t 1i t 

2. The process as set forth in claim 1 wherein the norbornenes are dissolved in a hydrocarbon solvent.
 3. The process as set forth in claim 2 wherein the norbornenes are dissolved in a carbocyclic solvent.
 4. The process as set forth in claim 3 wherein norbornene is treated.
 5. The process as set forth in claim 3 wherein 5-methyl-2-norbornene is treated.
 6. The process as set forth in claim 3 wherein 5-ethyl-2-norbornene is treated.
 7. The process as set forth in claim 3 wherein norbornadiene is treated.
 8. A process for the production of alkyl benzenes which comprises a. passing norbornenes, in the presence of from about 4 to about 12 moles of hydrogen per mole of hydrocarbon feed, at a LHSV of from about 0.5 to about 5.0 and a pressure from about 175 to about 300 psig through a hydrogenation catalyst effective to hydrogenate olefinic unsaturation at a temperature from about 100* to about 225*C., b. passing the effluent under the same LHSV and pressure conditions through a reforming catalyst effective to convert saturated carbocyclics to aromatics at a temperature from about 425* to about 525*C. and c. recovering the alkyl benzenes.
 9. The process as set forth in claim 8 wherein the norbornenes are dissolved in a carbocyclic solvent.
 10. The process as set forth in claim 7 wherein the norbornenes are dissolved in about 50 to about 90 mole percent of a carbocyclic solvent.
 11. The process as set forth in claim 7 wherein the carbocyclic solvent is cyclohexane.
 12. The process as set forth in claim 7 wherein the carbocyclic solvent is diethyl cyclohexane. 